The overall goal is to understand the molecular biology of the nuclear polyhedrosis virus (NPV) that infects the cotton bollworm, especially the control of transcription during infection. Toward this end, we propose to purify and characterize the mRNA for the major viral protein product, polyhedrin and to discover the timing of its synthesis during infection, using hybridization to polyhedrin cDNA. Next, we will determine whether purified host RNA polymerases can synthesize polyhedrin mRNA in vitro and if not, whether there are factors in infected cells that make possible such transcription. If factors are found, these will be characterized as to physical properties and mechanism of action. For example, do they promote tight binding between polymerase and viral DNA? We will also look for changes in the structures of the RNA polymerases during infection, using SDS- and urea-gel electrophoresis. The polymerases from infected cells will also be assayed for ability to read the polyhedrin gene. Finally, the polyhedrin gene will be placed on a physical map of the NPV genome.